30 BOVINE OBSTETRICS 



of intra-uterine life, increasing up to birth, and then diminishes 

 in size. At birth the thymus of the calf weighs 100 to 200 g. 



According to Ellenberger's "Anatomy," the atrophy of 

 the thymus is the result of fatty degeneration, gradually 

 extending from the surface to the interior, crowding upon the 

 follicles and causing atrophy. 



The thymus has a histological structure simulating lymph 

 glands, and is counted among the blood glands. 



THE GENITO-URINARY APPARATUS. 



The kidneys of the foetus are large and lobulated. The 

 Wolffian bodies, or primordial kidneys, have disappeared at 

 birth. The urinary bladder, by means of the urachus, is in 

 direct communication with the allantois. At birth, the um- 

 bilical cord tears, as also the urachus. The muscular layer of 

 the bladder contracts, thus obliterating the entrance into the 

 urachus. The testicles at the time of birth are already in the 

 scrotum. 



4.— The Intra-TJterine Position of the Foetus. 



In the beginning of pregnancy the foetus floats in the 

 amniotic liquid, and therefore does not occupy a distinct 

 position. Later, toward the end of gestation, its position is 

 more stationary, because the walls of the uterus apply them- 

 selves to the foetus. When only one calf is present, it rests 

 in one of the uterine horns ; when twins, usually each cornu 

 harbors one calf. Should both calves arise from the same 

 ovum, a common chorion but individual allantois and amnion 

 are found. In this case each foetus has its own circulation. 

 Observations show that under such conditions both foetuses 

 have the same sex. When the foetuses develop from several 

 eggs, each has its own chorion, and they are mostly of 

 different sex. 



Franck was of the opinion that the foetus has a defined 

 position at the outset of pregnancy. In numerous post 

 mortem examinations by him of the pregnant uteri of sheep 



